Your RT device should already come equipped with a media player, although if you want VLC media player you can get that
here.
To stream it from your computer, have you tried
sharing the folder with your media files on your desktop and then accessing it from your surface?
Technically if you wanted to, you could create a shared folder on your surface
using this, and then copy the files you want watch directly onto the surface device itself.
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If you stream videos to your devices often, I highly recommend you install
Plex Media Server. You install the Server on your desktop with all your videos, and then you install the
client onto your Surface tablet. Think of it as a sort of personal netflix, only it gets its content from your computer, which you provide yourself.